1. Field of Art
This disclosure generally relates to fiber based optical parametric oscillators.
2. Description of the Related Art
Light sources based on optical parametric interaction are interesting since they provide access to laser wavelengths that existing gain materials based on electronic transitions cannot provide. An optical parametric oscillator (OPO) can be realized by exploiting the χ(2) nonlinear optical response in a wide range of crystals or the χ(3) nonlinear response in optical fibers.
Optical fiber based OPO (FOPO) are particularly attractive owning to their potential in achieving low cost, alignment-free and compact laser systems while still providing very wide tuning range and high power operation.
The operation of FOPOs is in essence based on degenerated four-wave-mixing (FWM) wherein two pump photons interact with the fiber to generate a signal photon and an idler photon. The exact frequencies of the signal and idler photons are defined by the phase matching condition which depends on the pump laser wavelength, its peak power as well as the dispersion profile of the optical fiber. There are two common ways to pump an OPO. The first approach is continuous pumping where the pump laser is a continuous wave laser or a laser generating long pulses compared to the OPO cavity round trip time. The second approach is based on synchronous pumping of pulsed pump laser. In the second approach, the pump laser is synchronized with the OPO cavity.
Ultrafast synchronously pumped FOPOs have been demonstrated in the past. However, the output pulse energy and peak power of past FOPO have been quite modest. The best ultrafast FOPO that has been produced in the past in terms of output pulse energy and peak power was up to 2 nJ pulse energy and ˜12 kW peak power). The technique used to achieve this was to use only 2 cm fiber length and the rest of the cavity was free-space optics. This implementation avoided the adverse influence of nonlinear effects but required the use of mostly free-space components so free-space alignment was required, and the problems that go along with such a system. What is needed is a high power ultrafast FOPO in an all-fiber laser cavity or mostly all-fiber laser cavity. What is also needed is an ability to tune the emission wavelength of the FOPO over a wide rage while providing high output pulse energy.